Cross-culturally? Would the similar results be obtained in Ireland, Poland, Russia? Perhaps my generalizations are somehow better match to reality?
You're probably unaware, but some regions has tradition of alcohol consumption deep in their culture and even national identity and nearly everyone consumes alcohol to various degrees.
New Zealand is one of those places.
> nearly everyone consumes alcohol to various degrees.
That's the point of the study. Wealthy people consume alcohol in moderate amounts, the working class are likely:
1) Consuming it in much greater amounts, or
2) Abstaining from alcohol entirely. Perhaps because of previous problems with alcohol abuse, strict religious adherence, etc. You can think of multiple reasons that might explain seeing such a class disparity.
New Zealand is one of those places.